Using SV40 as a model for infection by DNA viruses, the proposed studies will contribute to our understanding of the role that epigenetics plays in determining the fate of viral chromatin during the initiation of an infection. Our central hypothesis is that DNA viruses organized into chromatin contain histone modifications that activate competing cellular processes during the early stages of infection which result in either activation of viral transcription or inactivation of the incoming chromatin. The specific aims are: (1) To characterize the SV40 epigenomes present in virions and minichromosomes during the initiation of infection, (2) To correlate changes in the epigenomes of minichromosomes with the initiation of early transcription, and (3) To characterize the role of epigenetic modifications present in viral chromatin in the establishment of a subsequent infection. The histone modifications present in the epigenomes of SV40 chromatin from virions and minichromosomes isolated early in infection or undergoing activation of transcription will be determined using various ChIP procedures. The SV40 epigenomes will be defined by the presence of distinct combinations of histone modifications and correlated with the activation of early transcription. The role of epigenetic modifications in determining the fate of an infecting SV40 minichromosome will be analyzed by inhibiting histone methylation with siRNAs targeting the relevant histone methylases and characterizing the effects of inhibition on virion formation and establishment of an infection. The proposed work is innovative, because for the first time the role of epigenetic regulation in defining the histone modifications present in viral chromatin and the subsequent fate of the infecting viral chromatin will be determined. The proposed work is significant for two reasons. First, understanding the role of epigenetics in determining the fate of chromatin infecting a cell may lead to therapeutic interventions designed to reduce or eliminate an infection. Second, confirmation of our central hypothesis would lead to a significant advance in our understanding of the role of epigenetics in regulating the competing viral and cellular processes necessary for the establishment of an infection. PUBLIC HEALTH RELEVANCE: The proposed studies will be the first characterization of the role of epigenetics in the establishment of a viral infection. The results obtained will significantly add to our knowledge of the role of histone modifications in the initiation of early transcription and the activation of cellular processes designed to limit infection. SV40 has been an excellent model to study basic eukaryotic molecular biology and the mechanisms underlying cellular transformation by DNA tumor viruses. The proposed research will extend this use as a model to the investigation of the role of epigenetic regulation in establishing a viral infection. The results obtained will be relevant to other viral human diseases and to a basic understanding of the mechanisms and functions of epigenetic regulation.